On Monday, February 03, 2014 at 12:06:59 PM, Lukasz Majewski wrote: > Hi Marek, > > > On Saturday, February 01, 2014 at 12:05:29 PM, Lukasz Majewski wrote: > > > On Sat, 1 Feb 2014 03:55:20 +0100 > > > > > > Marek Vasut <ma...@denx.de> wrote: > > > > On Friday, January 31, 2014 at 01:16:27 PM, Lukasz Majewski wrote: > > > > > The Samsung's UDC driver is not anymore copying data from USB > > > > > requests to data aligned internal buffers. Now it works > > > > > directly in data allocated in the upper layers like UMS, DFU, > > > > > THOR. > > > > > > > > > > This change is possible since those gadgets now take care to > > > > > allocate buffers aligned to cache line > > > > > (CONFIG_SYS_CACHELINE_SIZE ). > > > > > > > > > > Previously the UDC needed to copy this data to internal aligned > > > > > buffer to prevent from unaligned access exceptions. > > > > > > > > > > Test condition > > > > > - test HW + measurement: Trats - Exynos4210 rev.1 > > > > > - test HW Trats2 - Exynos4412 rev.1 > > > > > 400 MiB compressed rootfs image download with `thor 0 mmc 0` > > > > > > > > > > Measurement: > > > > > Transmission speed: 27.04 MiB/s > > > > > > > > > > Change-Id: I1df1fbafc72ec703f0367ddee3fedf3a3f5523ed > > > > > Signed-off-by: Lukasz Majewski <l.majew...@samsung.com> > > > > > Cc: Marek Vasut <ma...@denx.de> > > > > > > > > You should use ROUND_UP(), not ROUND() throughout the patch. > > > > Otherwise you might fail to flush/invalidate the last little bit > > > > of data in some cacheline. > > > > > > I might overlooked something, so please correct me if needed. > > > > > > I allocate buffers in gadgets which are aligned to cache line with > > > starting address and its size is a multiplication of cache line size > > > (so I will not trash data allocated next to it when I invalidate > > > cache). > > > > > > In the code I'm using ROUND to invalidate/flush more data than > > > needed (ROUND(176, 32) = 192). I'm prepared for this since buffer > > > in gadget is properly allocated (with DEFINE_CACHE_ALIGN_BUFFER() > > > which uses roundup() internally). > > > > The problem is in case you receive buffer which is aligned to > > cacheline with it's start, but is [(k * cacheline_size) + > > (cacheline_size / 2) - 1] big. I think it's unlikely, but if this > > happens, you will get corruption, right ? > > Let's suppose, that I will receive 2063B = [(64 * 32) + 16 -1] from UDC. > If the passed buffer was exactly 2063 B in size, then we would have > here a data corruption. > > However this situation will not happen
_Should_ not happen ... I am absolutelly positive someone will be bitten by such assumption. I think this assumption about buffer alignment should really be documented somewhere. > since the buffer at gadget is > allocated with DEFINE_CACHE_ALIGN_BUFFER() or is an aligned > multiplication of cache line size (like 1MiB). > > I think, that it is the responsibility of gadget developer to allocate > buffers with proper alignment and size. Document that please, I doubt this is documented anywhere, but it's clearly part of the API. Also, some checks might be put in place for the alignment , they might be in #ifdef DEBUG for all I care, but it would be nice to have such a check, since I'm worried someone will really be bitten. > > You might actually want to > > check for this condition and throw a warning in such a case. > > The check is already implemented at ./arch/arm/cpu/armv7/cache_v7.c. Yeah, for arm926ejs core as well. Maybe that check shall be shifted into the cache management routine prototypes somehow ... not all CPUs implement that check :-( > It complains with "ERROR" message when start or end address is not > aligned (that is how I've discovered the unaligned buffers at UMS). Yes. > > I understand your argument with trying to not trash data, but then > > you will get a corruption during transfer, right ? > > After applying those patches, the cache management would be performed > when the USB request is completed (in the UDC). > > The only requirement for UDC is the correctly allocated buffer at > gadget. Got it. _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
